When operating electrical and mechanical machines, it is important to ensure that the risk for accidents is minimized. In many applications, information on whether two different parts are in the vicinity of each other is of importance. For example, in many applications, it is important to know whether a lid or door to a machine has been opened or not, or if machine parts are in the correct position. An area wherein a dangerous machine is located can be enclosed by walls or by a fence, and information on whether or not the area has been entered by a person may be of importance for determining whether or not it is safe to operate the machine.
Proximity switches are typically used as position detectors which can detect whether one part is in the vicinity of another part. A proximity switch is a device which comprises two parts, and which detects when the two parts are in proximity of each other. A non-contact proximity switch is a proximity switch wherein the two parts do not need to be in contact with each other to detect proximity of the two parts. An example of a non-contact proximity switch is a radio-operated proximity switch, wherein the first part sends a radio signal as a query signal, which is detected by the second part if in proximity of the first part. The second part then sends a radio signal as a response signal, which is detected by the first part. Proximity of the two parts can thus be verified. The second part is sometimes referred to as the actuating part.
The present invention relates to an improved proximity switch, by which the operation of a machine safety system will be more efficient.
US 2012/152072 A1 discloses a safety system preventing an operator of a cutting machine from being accidentally carried through the infeed chute into the machine's cutting mechanism. By providing the operator a safety device, mounting a sensor array on opposing sides of the cutting machine's infeed chute, the magnetic field of the safety device is able to induce a current in the sensor array as it moves in the proximity of the sensor array. The safety system generates a signal which is proportional to the sum of the induced currents. When the signal exceeds a threshold, the safety system shuts off power to the feed mechanism and/or the cutting blades of the cutting machine, preventing injury to the operator.